From fb254e3f2c675ed65b78551224e3ed1115739f5c Mon Sep 17 00:00:00 2001
From: epipho <hiwrac@gmail.com>
Date: Sun, 26 Oct 2014 00:10:03 -0400
Subject: [PATCH] docker_version can now be left blank to automatically
 download and install the latest available. Docker client will not be
 installed if it is already present in the build container.

---
 plugin/publish/docker.go      | 23 ++++++++++++++---------
 plugin/publish/docker_test.go | 26 +++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/plugin/publish/docker.go b/plugin/publish/docker.go
index 5af0cb27..387d4439 100644
--- a/plugin/publish/docker.go
+++ b/plugin/publish/docker.go
@@ -15,7 +15,7 @@ type Docker struct {
 	// Connection information for the docker server that will build the image
 	// Same format than DOCKER_HOST envvar, i.e.: tcp://172.16.1.1:2375
 	DockerHost string `yaml:"docker_host"`
-	// The Docker client version to download. This must match the docker version on the server
+	// The Docker client version to download. Will default to latest if not set
 	DockerVersion string `yaml:"docker_version"`
 
 	// Optional Arguments to allow finer-grained control of registry
@@ -38,27 +38,32 @@ type Docker struct {
 }
 
 // Write adds commands to the buildfile to do the following:
-// 1. Install the docker client in the Drone container.
+// 1. Install the docker client in the Drone container if required.
 // 2. Build a docker image based on the dockerfile defined in the config.
 // 3. Push that docker image to index.docker.io.
 // 4. Delete the docker image on the server it was build on so we conserve disk space.
 func (d *Docker) Write(f *buildfile.Buildfile) {
-	if len(d.DockerHost) == 0 || len(d.DockerVersion) == 0 || len(d.ImageName) == 0 {
+	if len(d.DockerHost) == 0 || len(d.ImageName) == 0 {
 		f.WriteCmdSilent(`echo -e "Docker Plugin: Missing argument(s)\n\n"`)
 		if len(d.DockerHost) == 0 {
 			f.WriteCmdSilent(`echo -e "\tdocker_host not defined in yaml"`)
 		}
-		if len(d.DockerVersion) == 0 {
-			f.WriteCmdSilent(`echo -e "\tdocker_version not defined in yaml"`)
-		}
 		if len(d.ImageName) == 0 {
 			f.WriteCmdSilent(`echo -e "\timage_name not defined in yaml"`)
 		}
 		return
 	}
-	// Download docker binary and install it as /usr/local/bin/docker
-	f.WriteCmd("wget -qO- https://get.docker.io/builds/Linux/x86_64/docker-" +
-		d.DockerVersion + ".tgz |sudo tar zxf - -C /")
+
+	// If docker version is unspecified, download and install the latest client
+	if len(d.DockerVersion) == 0 {
+		d.DockerVersion = "latest"
+	}
+
+	if len(d.DockerVersion) > 0 {
+		// Download docker binary and install it as /usr/local/bin/docker if it does not exist
+		f.WriteCmd("type -p docker || wget -qO- https://get.docker.io/builds/Linux/x86_64/docker-" +
+			d.DockerVersion + ".tgz |sudo tar zxf - -C /")
+	}
 
 	dockerPath := "."
 	if len(d.Dockerfile) != 0 {
diff --git a/plugin/publish/docker_test.go b/plugin/publish/docker_test.go
index 5263461b..ffee8985 100644
--- a/plugin/publish/docker_test.go
+++ b/plugin/publish/docker_test.go
@@ -35,7 +35,7 @@ publish:
 
 func TestDockerHost(t *testing.T) {
 	response, err := setUpWithDrone(dockerHostYaml)
-	t.Log(privateRegistryNoAuthYaml)
+	t.Log(dockerHostYaml)
 	if err != nil {
 		t.Fatalf("Can't unmarshal script: %s\n\n", err.Error())
 	}
@@ -50,6 +50,30 @@ func TestDockerHost(t *testing.T) {
 	}
 }
 
+var dockerHostNoVersionYaml = `
+publish:
+  docker:
+    docker_host: tcp://server:1000
+    image_name: registry/image
+`
+
+func TestDockerHostNoVersion(t *testing.T) {
+	response, err := setUpWithDrone(dockerHostNoVersionYaml)
+	t.Log(dockerHostNoVersionYaml)
+	if err != nil {
+		t.Fatalf("Can't unmarshal script: %s\n\n", err.Error())
+	}
+	expected := "export DOCKER_HOST=tcp://server:1000"
+	if !strings.Contains(response, expected) {
+		t.Fatalf("Response: " + response + " doesn't export correct " +
+			"DOCKER_HOST envvar: expected " + expected + "\n\n")
+	}
+	download := "https://get.docker.io/builds/Linux/x86_64/docker-latest.tgz"
+	if !strings.Contains(response, download) {
+		t.Fatalf("Response: " + response + " doesn't download from:" + download + "\n\n")
+	}
+}
+
 // Private Registry Test (no auth)
 var privateRegistryNoAuthYaml = `
 publish: